MVC的概念，大家都清楚吧，Model，View，Control
首先我们看看这个目录结构
--+login
----------+WEB-INF
-----------------------+classes
-beans
-tags
-----------+tlds
login 是主目录放jsp文件，在例子login.jsp，loginFailed.jsp，login_form.jsp，newAccount.jsp，welcome.jsp，accountCreated.jsp
Web-inf下面有web.xml配置文件，classes文件夹放类，tlds文件夹放自定义标签
由于我没有用到数据库，所以没有用LIB文件夹，是来放置 *.jar 文件的。
classes目录下，有beans，tags文件夹，分别放置User，LoginDB类，和自定义标签类GetRequestParameterTag，classes目录下还直接放了LoginServlet，NewAccountServlet控制器类
我们先看beans下的两个业务对象类
User.java
package beans;
public class User implements java.io.Serializable {
private final String userName, password, hint;
//final强调此属性初始化后，不能修改hint是口令提示
public User(String userName, String password, String hint) {
this.userName = userName;
this.password = password;
this.hint = hint;
}
public String getUserName(){
return userName;
}
public String getPassword(){
return password;
}
public String getHint(){
return hint;
}
//判断当前对象用户名和密码是否相等
public boolean equals(String uname, String upwd) {
return getUserName().equals(uname) && getPassword().equals(upwd);
}
}
LoginDB.java
package beans;
import java.util.Iterator;
import java.util.Vector;
public class LoginDB implements java.io.Serializable {
private Vector users = new Vector();
//Vector类是同步的，所以addUser就不需要同步了
public void addUser(String name, String pwd, String hint) {
users.add(new User(name, pwd, hint));
}
//下面方法判断是否存在正确的user
public User getUser(String name,String pwd) {
Iterator it = users.iterator();
User user;
//迭代需要同步
synchronized(users) {
while(it.hasNext()){
user = (User)it.next();
if(user.equals(name,pwd))
return user; //如果返回真，就返回当前user
}
}
return null;
}
public String getHint(String name) {
Iterator it = users.iterator();
User user;
synchronized(users) {
while(it.hasNext()){
user = (User)it.next();
if(user.getUserName().equals(name))
return user.getHint();
}
}
return null;
}
}
login.jsp
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>Login Page</title>
</head>
<body>
<%@ include file="login_form.jsp" %>
</body>
</html>
被包含的login_form.jsp
<%@ taglib uri="utilities" prefix="util" %>
<!--调用自定义标签，引用为util，uri的utilities在web.xml映射了-->
<p><font color="#6666CC">请登陆</font></p>
<hr>
<form name="form1" method="post" action="<%=response.encodeURL("login")%>"><!--login是LoginSevlet通过在web.xml映射了-->
<table width="68%" border="0" cellpadding="2" cellspacing="2">
<tr>
<td width="33%" align="right">用户名：</td>
<td width="67%">
<input type="text" name="userName" value="<util:requestParameter property='userName'/>"></td><!--注意这里用了自定义标签，如果有值就显示-->
</tr>
<tr>
<td align="right">密码：</td>
<td><input type="text" name="userPwd" ></td>
</tr>
<tr align="center">
<td colspan="2">
<input type="submit" name="Submit" value="登陆">
</td>
</tr>
</table>
</form>
LoginServlet.java
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;
import beans.User;
import beans.LoginDB;
public class LoginServlet extends HttpServlet {
private LoginDB loginDB;
public void init(ServletConfig config) throws ServletException {
super.init(config);
loginDB = new LoginDB();
config.getServletContext().setAttribute("loginDB",loginDB);
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException{
String name = request.getParameter("userName"); //从login_form 表单得到值
String pwd = request.getParameter("userPwd");
User user = loginDB.getUser(name,pwd);
if(user != null){ //说明存在用户
request.getSession().setAttribute("user",user); //放到session 里面
request.getRequestDispatcher(response.encodeURL("/welcome.jsp")).forward(request,response); //成功转发到welcome.jsp
}else{
request.getRequestDispatcher(response.encodeURL("/loginFailed.jsp")).forward(request, response);
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException{
doGet(request,response);
}
}
web.xml添加
<servlet>
<servlet-name>Login</servlet-name> <!--名字-->
<servlet-class>LoginServlet</servlet-class> <!--指定类-->
</servlet><servlet>
<servlet-name>new_account</servlet-name>
<servlet-class>NewAccountServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>new_account</servlet-name>
<url-pattern>/new_account</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Login</servlet-name> <!--和上面的名字一致-->
<url-pattern>/login</url-pattern> <!--映射路径-->
</servlet-mapping>
<taglib>
<taglib-uri>utilities</taglib-uri>
<taglib-location>/WEB-INF/tlds/utilities.tld</taglib-location>
<!--自定义标签的实际位置-->
</taglib>
utilities.tld关键部分
<taglib>
<tag>
<name>requestParameter</name>
<tagclass>tags.GetRequestParameterTag</tagclass>
<!--类的位置，如果有包写上-->
<info>Simplest example: inserts one line of output</info>
<bodycontent>Empty</bodycontent>
<attribute>
<name>property</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
自定义标签类GetRequestParameterTag.java
package tags;
import javax.servlet.ServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class GetRequestParameterTag extends TagSupport {
private String property;
public void setProperty(String property){
this.property = property;
}
public int doStartTag() throws JspException {
ServletRequest reg = pageContext.getRequest();
String value = reg.getParameter(property);
try{
pageContext.getOut().print(value == null ? "":va
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